Process of manufacturing a waterlaid felt



Patented Apr. 23, 1940 UNITED STATES PROCESS OF MANUFACTURING A WATER- LAID FELT Henry Philip Shopneck, New York, N. Y.

No Drawing. Application November 15, 1938, Serial No. 240,509

4 Claims.

Various substitutes have been proposed for the expensive wool felt used in box toe stock in an effort to produce a low-cost, durable box toe material which will be sufficiently absorbent to 5 take up and retain the thermoplastic binder, which will possess sufficient tensile strength to hold its shape under the severe strains in lasting the shoe, and which will not only have capacity for stretch to assume the shape of the toe, but

will be sufficiently resilient to return to shape after compression. The expensive wool felt is quite smooth, but all substitutes heretofore proposed lack the very essential quality of smoothness.

- Felts containing hair, jute, ramie, or other long fibres distributed throughout a short fibred rag or textile rag base, and in felted relation therewith, have been proposed, but all result in a felt insufiiciently smooth due to the presence 30 of lumps, nubs, unbeaten or undisintegrated clumps of fibres (buttons, rubber material, etc.,) said lumps, nubs, or undisintegrated clumps of fibres, etc., being present due to the inability to screen the mixture of long and short fibres,

25 such screening inevitably resulting in the removal of all the desirable and necessary long fibre along with the undesirable foreign matter heretofore mentioned. Upon saturating the usual felt made from a mixture of long and short fibre, the lack 30 of uniformity and smoothness, due to the inability to screen the mixture, results in the saturant being ununiformly distributed through the base felt and on the surface layers thereof, resulting in easy rupture of the toe when lasted 35 and in lack of stretch when pulled over the last.

An additional feature of my present invention is to make possible a sheet of substantially uniform absorbency. In the usual process of manufacturing a felt composed of a mixture of long l0 and shorter fibres, the initial beating of the shorter fibres to smoothness results in a felt the shorter fibre portion of which is composed of short fibres of varying lengths, some very short, almost powdery, some slightly longer and the l5 rest of the optimum desired length. Since the base fibre used varies, as no two lots of raw stock are alike, the final felt obtained varies enormously in porosity. By this process, this defect is eliminated and a felt of substantially ;0 uniform porosity and density and absorbency is obtained, as the shorter fibres are selectively screened using screen slots of the desired length and width, so as to give a short fibre base, the longest and shortest of which cannot possibly 5 retard the absorbency of the felt resulting, therefore, in a smooth felt of substantially uniform absorptive character.

Likewise, in the saturated roofing and flooring industries, it has been found desirable to incorpo- 0 rate a long fibre throughout the short-fibred base and in felted relation therewith. Here again, however, the inability to screen out the undesirable foreign matter usually found in a mixture of the longfibres and the rags commonly used in manufacturing roofing and flooring felt, such as buttons, seams, rubber, metal particles, etc., without removing the very desirable longer fibres, makes necessary the sheeting out of the stock on a-paper machine without screening. Such a felt, although strong, tough and durable, lacks the highly essential element of smoothness, making uniform surfacing and uniform coatings impossible. This is likewise done in the case of feltsintended for saturation with rubber or rubber latex, cellulose-ester Celluloid, etc.

To the end therefore of producing a saturation vehicle for box toes, roofing, flooring, Celluloid impregnated products, rubber saturated products and similar impregnated products, which will embody all of the foregoing requisites and yet present a smooth surface, I have devised my present invention. According to it I take a short fibred stock, such as waste textile rags (mixed rags containing more or less wool) or a mixture of such rags and wool or other fibres, or new and/or old cotton rags and/or other fibres and beat out until smooth, either in an ordinary paper makers beater, or rod mill or similar disintegrating fiberizer, the disintegrating taking place according to regular paper making practice in an aqueous medium.

Then I screen the beaten short fibre in the usual papermakers fashion, as by passing the wet pulpy mass of short fibres, containing the usual undesirable foreign matter, through a flat slotted plate screen, or through a slotted rotary screen. To this wet mass of screened short fibre, now substantially free of its undesirable foreign elements, I add much longer unscreened fibre, such as hair jute, ramie, etc. I then sheet out the mixture of screened short fibre and un screened long fibre on a paper machine, but I may prior thereto, and in fact it desirable, to first brush it out in the beater or by means of a Jordan engine or like machine, taking due precautions not to unduly shorten the fibres of the mixture. A

Also, I may beat out the short fibred stock in an aqueous medium, screen the wet pulpy shortfibred mass to remove undesirable foreign matter, then thicken it by means of a papermakers save-allffilter, or screw-press, then admix the screened and thickened short fibre, with the unscreened longer fibre, said admixing of the short and relatively longer fibres taking place preferably in a beater to which the screened and thickened short-fibred stock has been returned, and finally sheet out on a paper machine, the mixture of screened short fibres and unscreened relatively longer fibres with or without previously brushing out the mixture in the beater or jordan.

To further remove foreign matter from the short fibres, or the relatively longer fibres or the mixture thereof, I'may pass each of them or a mixture of them in a water suspension over a rifile and/or sand trap.

A satisfactory felt is obtained by using jute, hair, or ramie, fibre of about an inch, or inch and a quarter in length and a very much shorter textile rag fibre or mixture of cotton and wool rags, or new cotton rag cuttings of about 75%, depending upon whether it is to be used for box toe felt, roofing felt, flooring felt, rubber saturated products, etc. If desired, I may increase the proportion relatively of longer fibre to the shorter textile rag, or other suitable short fibre while retaining all the advantages of increased strength, and stretch, and smoothness.

By sheeting out on a paper machine, I mean to include sheeting out the fibres in the old usual way on a Fourdrinier, cylinder machine, wet machine, combinations of such machines, or similar watermedium felting machines adaptable for sheeting out fibrous pulp.

In order that a smooth, uniform sheet may be prepared by the use of,the aforementioned machines, the fibres of the short-fibred portion of the pulpy mass are usually fairly short, the actual length varying with different fibres. For example, ground wood fibres are of the order of 3 or 4 millimeters in length, while chemically cooked wood fibres may approach 6 or I millimeters in length. Rag fibres derived from cotton or linen material may be somewhat longer, and still be suitable for the preparation of smooth, uniform sheets. The width of the screening slots will vary according to the fibre used from, say, 0.014 inch to 0.40 or even wider.

My present invention contemplates the use of various fibres, of various lengths, and of animal, vegetable, and mineral origin which I have found can be used as the base of a saturation product, such fibres being blended, in the presence of water with other fibres, formed in a sheet, and serving as a vehicle for various impregnating compounds.

For example:

Reasonably short-beaten new cotton cuttings- 70 Long cotton fibre (%-1 long) Composed of unravelled fibre bundles.

In the preparation of the felt, it is essential that some reasonably short fibres be present, the

to either entwinement around, between, or by the short fibres; or by virtue of their nature, be susceptible of felting in the presence of water, through the aforementioned assistance of a papermakers wire, either with other long fibres or with the short fibres.

The length of the long fibres initially may be controlled by the length in which they are originally found, as in the case of animal hair, cotton slivers, etc., or the length may be controlled by a textile picking operation, or by pretreatment in a rag cutter, and finally, also by beater treatment thereof or subsequent treatment in the Jordan engine or hydra refiner. y

In certain paper felt industries, like the box toe felt industry, it has become the practice to subject the fibres to a textile picker operation, for the dual purpose of shredding the stock and removing as much of the foreign matter as possible. By the above mentioned short-fibre screening process, this textile picker treatment becomes unnecessary, resulting in a considerable saving, while at the same time greatly improving the smoothness of the felt.

The relative lengths of the short and long fibres may be governed, first, by the initial length. of the fibre used, second, by the pretreatment given it, that is, textile picking, cooking, cutting, halfstocking, or beater treatment in the judicious handling of the roll. The relative percentages ofthe long and short fibres should be so adjusted to give the impregnated'material the maximum strength, and so as to enable the saturation vehicle, or fibrous product, to be saturated without tearing, and to withstand the rigors of coating and embossing.

Further, and what is highly important, is that the percentages of long and short fibre be so regulated as, in addition to running well on the sheeting machine, the proportion of short fibre be sufiicient to carry the longer fibres, in the case where non-hydratable fibres are used for the long fibre content, such as hair, wool, leather asbestos (long), elongated ligno-cellulose fibres, such as jute, hemp, etc.; and in the case of the long hydratable fibres, such as cotton, ramie, rope stock, etc., including certain types of long but hydrated vegetable-origin fibres, the percentage of short fibres should be so regulated as to result in a soft, porous, highly absorbent material, which after impregnation will be very strong.

By the expression relatively short fibre" or short fibre, I mean the usual length of fibre commonly used in the preparation of ordinary papers or felts. By the expression relatively long fibre or long fibre I mean fibres whose length is greater than that commonly used in the'preparation of ordinary papers and waterlaid materials for paper purposes, being approximately of the order hereinbefore cited. or course considerable latitude must be allowed in the actual length of fibres used due to the variations present in the commercially available raw materials.

Further, by the use of the term short fibre I mean short with respect to the usual length of fibre encountered in the textile industry, and by the use of the term long fibre I mean long with respect to the usual length of fibre encountered in the paper industry.

It is immaterial whether the fibres are new, such as cotton fibre fresh from the plant, or assumes the form of new cotton cuttings such as new shoe rags, or shoe rag cuttings, or come 15 from old or new textile rags, or constitute a waste or old product.

All such and related variants are to be considered as within the scope and purview of my invention as defined in the appended claims.

Impregnated products prepared from felts formed from a felted mixture of screened short fibre and unscreened relatively longer fibre, saturated with a loading agent, have been found to have new and unexpected smoothness, and an accompanying evenness in stretch and strength.

By the term loading agent, I mean, for example, any general saturant for felts such as:

((1) Shoe stiifening agents: (thermoplastic binders, Celluloid, cellulose acetate or cel1uloseester).

(b) Roofing and flooring felt saturants: asphalts, waxes, resins, pitches, bitumens, pyrobitumens, asphaltites or suitable mixtures thereof.

.(c) Rubber latex or rubber dispersion saturants.

In the appended claims the term "water-laid refers to a fibrous product, the fibres of which have been sheeted out in an aqueous medium, as,

by means of a Fourdrinier, cylinder-machine, wetmachine, or combinations of these or similar machines.

All such and related variants are to be considered as within the scope and purview of my invention as defined in the appended claims.

What I therefore claim and desire to secure by Letters Patent is:

1. A process of preparing water-laid felts composed of a mixture of long and short fibres, as described, comprising the successive steps of beating out in an aqueous medium the stock constituting substantially the short-fibred portion, screening said wet short-fibred stock, admixing the relatively longer fibre therewith, and finally sheeting out the wet pulpy mass by means of a paper machine.

2. A process of preparing water-laid felts composed of a mixture of long and short fibres, as described, comprising the successive steps of beating in an aqueous medium, screening, and thickening the wet stock constituting substantially the short fibred portion, admixing the relatively longer fibre therewith, and finally sheeting out the wet pulpy mass by means of a paper machine.

3. A process of preparing water-laid felts composed of a mixture of long and short fibres, as described, comprising the successive steps of beating out in an aqueous medium the stock constituting substantially the short-fibred portion, screening said wet short fibred stock, admixing the relatively longer fibre therewith, brushing out the mixture, as described, and finally sheeting out the wet pulpy mass by means of a paper machine.

4. A process of preparing water-laid fibrous product composed of a mixture of long and short fibres, as described, comprising the successive steps of beating in an aqueous medium, screening and thickening the wet stock constituting substantially the short-fibred portion, admixing the relatively longer fibre therewith, brushing out the mixture, as described, and finally sheeting out the wet pulpy mass by means of a paper machine.

HENRY PHILIP SHOPNECK. 

